Quote:
Originally Posted by SooMe
It says "The prior distribution for sigma squared is expontential with mean 1.25." I take this to imply that sigma squared is therefore (1.25)^2 (variance = mean squared for exponential), but the solution says v = E(sigma^2) = 1.25. What... the F.

I'm not sure what the notation means, but as to what you wrote, I don't understand . sigma squared represents a variance, but the expected value of that variance is 1.25. That's what they tell you.
sigma squared isn't a single number; it has a distribution (an exponential distribution in particular). So since you cannot know what sigma squared
is (its numeric value), you must decide what you do need to know about sigma squared: its expected value or its variance. The SOA solution says you want to know its expected value.